Corte Madera, Calif. – Politicians and automakers say a car that can reduce greenhouse gases and free America from its reliance on foreign oil is years or even decades away.

Ron Gremban says such a car is parked in his garage.

It looks like a typical Toyota Prius hybrid, but in the trunk sits an 80- miles-per-gallon secret: a stack of 18 brick-sized batteries that boosts the car’s high mileage with an extra electrical charge so it can burn even less fuel.

Gremban, an electrical engineer and committed environmentalist, spent several months and $3,000 tinkering with his car.

Like all hybrids, his Prius increases fuel efficiency by harnessing small amounts of electricity generated during braking and coasting. The extra batteries let him store extra power by plugging the car into a wall outlet at his home in this San Francisco suburb, all for about a quarter.

He’s part of a small but growing movement. “Plug-in” hybrids aren’t yet cost-efficient, but some of the dozen known experimental models have gotten up to 250 mpg.

They have support not only from environmentalists but also from conservative foreign-policy hawks who insist that Americans fuel terrorism through their gas-guzzling.

And while the technology has existed for three decades, automakers are beginning to take notice too.

So far, DaimlerChrysler is the only company that has committed to building its own plug-in hybrids, quietly pledging to make up to 40 vans for U.S. companies. But Toyota officials who initially frowned on people altering their cars now say they may be able to learn from them.

“They’re like the hot-rodders of yesterday who did everything to soup up their cars,” said Cindy Knight, a Toyota spokeswoman. “Maybe the hot-rodders of tomorrow are the people who want to get in there and see what they can do about increasing fuel economy.”

The extra batteries let Gremban drive for 20 miles with a 50- 50 mix of gas and electricity. Even after the car runs out of power from the batteries and switches to the standard hybrid mode, it gets the typical Prius fuel efficiency of around 60 mpg. As long as Gremban doesn’t drive too far in a day, he says, he gets 80 mpg.

“The value of plug-in hybrids is they can dramatically reduce gasoline usage for the first few miles every day,” Gremban said.

Backers of plug-in hybrids acknowledge that the electricity to boost their cars generally comes from fossil fuels that create greenhouse gases, but they say that process still produces far less pollution than oil.

They also note that electricity could be generated cleanly from solar power.

Gremban rigged his car to promote the nonprofit CalCars Initiative, a San Francisco Bay Area-based volunteer effort that argues automakers could mass produce plug-in hybrids at a reasonable price.

But Toyota and other car companies say they are worried about the cost, convenience and safety of plug-in hybrids.

Automakers also have spent millions of dollars telling motorists that hybrids don’t need to be plugged in and don’t want to confuse the message.

Southern California-based Energy CS has converted two Priuses to get up to 230 mpg by using powerful lithium ion batteries. It is forming a new company, EDrive Systems, that will convert hybrids to plug-ins for about $12,000 starting next year.

University of California-Davis engineering professor Andy Frank, who has built a plug-in hybrid that gets 250 mpg, said that although automakers’ promise of hydrogen-powered vehicles has been hailed by President Bush, hydrogen’s backers admit the cars won’t be widely available for years and would require new fueling stations.

Giving a hybrid a jolt

What he did: Gremban added 18 brick- sized batteries, which allow him store extra power by plugging his car into an outlet at his home.

What it does: The extra electric boost increases his mileage to as much as 80 mpg

What it cost: About $3,000

Tax credits

Some tax credits beginning next year for the purchase of gasoline-electric vehicles:

More in Business

Fast forward to today, and Larkburger is celebrating its 10th anniversary, having grown from one restaurant in Edwards to 12 locations in the state amid increasingly fierce competition in the “better burger” world.

On the day President-elect Donald Trump lashed out at Boeing for the cost of replacing Air Force One, mechanics and engineers at the planemaker’s South Carolina factory were focused on another challenge: making the first 787-10 Dreamliner.

The trucking industry scored a victory this week when Republican lawmakers effectively blocked Obama administration safety rules aimed at keeping tired truckers off the highway. But there’s more coming down the road.